Pregnancy is a miraculous journey that spans around 40 weeks and is divided into three trimesters. Each stage brings about incredible changes in your baby’s development. Understanding how your baby grows inside the womb helps you stay connected to your pregnancy and prepares you for the exciting arrival of your little one.

In this article, we break down baby’s development at every major stage of pregnancy in a simple and easy-to-follow guide.

First Trimester (Weeks 1–12)

Weeks 1–4: The Beginning

• What’s Happening: It starts with fertilization, when a sperm meets an egg. The fertilized egg (zygote) travels down the fallopian tube and implants itself in the uterine lining.

• Baby's Size: About the size of a poppy seed.

• Development: The embryo forms, and basic structures like the placenta and umbilical cord begin to develop.

Weeks 5–8: Major Organs Start to Form

• Baby's Size: By week 8, about the size of a raspberry.

• Development: Heart starts beating. Brain, spinal cord, and major organs begin to form. Tiny arm and leg buds appear.

Weeks 9–12: Baby Takes Shape

• Baby's Size: Around the size of a plum.

• Development: Facial features become more defined. Fingers and toes are visible. The baby can make small movements, though you won’t feel them yet.

Second Trimester (Weeks 13–26)

Weeks 13–16: Feeling More Real

• Baby's Size: Around the size of an avocado.

• Development: Bones are hardening, and the baby begins to make sucking motions. Gender may be visible on an ultrasound.

Weeks 17–20: Movement and Senses

• Baby's Size: About the size of a banana.

• Development: Baby can hear sounds and may respond to your voice. You might feel the first flutters, known as “quickening.”

Weeks 21–26: Gaining Strength

• Baby's Size: About the length of a carrot.

• Development: Eyelids start to open. Taste buds develop. The baby practices breathing movements, even though lungs aren’t fully ready yet.

Third Trimester (Weeks 27–40)

Weeks 27–32: Rapid Growth

• Baby's Size: Around the size of a squash.

• Development: Baby’s brain and lungs continue maturing. Kicks and movements become stronger and more frequent.

Weeks 33–36: Getting Ready for Birth

• Baby's Size: Around the size of a honeydew melon.

• Development: Bones are fully developed, though still soft. The baby starts settling into a head-down position for birth.

Weeks 37–40: Final Stages

• Baby's Size: About the size of a small watermelon.

• Development: Baby is considered full-term at 37 weeks. Lungs are ready to breathe outside air. Fat stores increase, helping to regulate body temperature after birth.

Conclusion

From a tiny cluster of cells to a fully-formed baby, each week of pregnancy brings about new and exciting developments. Understanding what’s happening inside your womb not only deepens your bond with your growing baby but also helps you stay informed and empowered throughout your pregnancy journey.

Tip: Keep up with prenatal appointments and ask your doctor questions about your baby’s growth at each stage. Every pregnancy is unique, but knowing the typical milestones can help guide and reassure you.